[Imp]

What you are doing is giving them better protection vs dedicated AAA units, no effect vs regular units that don't infact have an EW rating.

The game tests respective EW of firer & target to determine hit chance, you see a message something like EW defeats missile & a big drop in hit chance. Then you get a check to see if the pilot evades & a similar result.

EW does fall down with regard to ATGMs as they ignore it & hence normally have a good hit chance but its pretty rare to find a stationary target for them so its not a huge issue.